Programming test 2 - C++ (part 3)

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Explicit Conversion

Can be used to remove warnings - you are effectively saying, "I know what I'm doing"

Characters

Can perform comparisons (lexicographical) Can perform arithmetic Can convert between cases

Valid Names

Cannot be a reserved word

Valid Names

Cannot begin with a number

Scope

Cannot have two variables in the same scope with the same name

Equal: == Not equal: != Less than: < Greater than: > Less than or equal to: <= Greater than or equal to: >=

Comparison Operators

Valid Names

Contain only letters, numbers, and underscores (_)

Streams

Data "flowing" from one place to another

Number Text Boolean

Data Types in OVERFLOW

assign or math

Data conversion occurs when you assign or math

Input Stream

Data flowing into the program By default comes from the keyboard The cin object

Input extraction

Only reads characters that matches the type of input we're looking for (e.g. digits for a number)

Boolean Operators

Operands must be boolean Answer is boolean && and || use short-circuit evaluation

Arithmetic/math Operators

Operands must have the same type Answer is always the same type as the operands Beware integer division Beware division by zero

Comparison Operators

Operands must have the same type Answer is boolean Beware equal / not equal with floats

associativity

Operators with the same precedence have an ______: either left associative (left-to-right) or right associative (right-to-left)

How do we decide which operation to perform first?

Parentheses Precedence & Associativity

Initialization

When you declare a variable, it's initial value is undefined; whatever happened to be in that memory previously; garbage

Const

can be initialized but not assigned to

Input

cin - key board

Input

cin >> variable;

Expression

consists of literals variables and operators

Declaration ****

consists of the data type, followed by the variable name (ends in semicolon)

Output

cout - screen

Output

cout << variable << data << endl;

Post-test loop

do block while (test); Must have a semi colon at the end

backslash

we use ___ for special characters

Pre-test loop

while (test) block

Literals

write data into program, literally; writing data directly into your program

higher

x / have _____ precedence than +-

{block} (Sequence)

{ instruction; instruction; ... }

Implicit conversion when performing a mathematical operation

— the two operands must be the same data type Smaller ⇒ larger Signed ⇒ unsigned Integer ⇒ floating point

I/O Manipulators

set width , set precision, set fill

Inputting a character

simply gives you the next character (its ASCII value)

Output strings

simply prints each character in sequence

using namespace std;

so you don't have to call by last name

void main()

sub routine named main

Input Strings

take multiple characters up until the next whitespace (single word)

Input numbers

takes as many number characters as it can find, then gives you the number with that value

Conversion

tries to copy the data to a different format

Assignment

variable = data;

Scope

From the point of declaration to the end of the block

Implicit Conversion

When assigning data of one type to a variable of a different type

short/long

(potentially) use less or more memory

Floating point rounding errors

-All numbers are represented in scientific notation -Decimal numbers do not make pretty binary fractions .1 = .00110011001100110011... -Fractions have to be rounded -Small changes may be lost 1e10 + 500 = 1e10

short int

2 bytes

long int

4 bytes

long double **

8 bytes

Whitespace Case sensitive #include <iostream> using namespace std; void main() Comments Text file

Basic forms of a C++ program

And: && Or: || Not: unary !

Boolean Operators

Namespaces

Acts as a "last name" to avoid accidental name conflicts

Input / Output Operators

Also has a side effect: input or output Left hand operand must be input/output stream Result is the stream

Explicit Conversion

Applies to the next piece of data

Add: + Subtract: - Multiply: * Divide: / Modulus (remainder): % Negative: unary -

Arithmetic/math Operators

Conversion

Assigning to a variable of a different type

Assign: = Add to: += Subtract from: -= Multipy by: *= Divide by: /= Increment: ++ Decrement: --

Assignment Operators

side effect

Assignment operators with a ____: Changes the variable

Error Stream

Data resulting from errors flowing out of the program By default goes to the screen The cerr object

Output Stream

Data resulting from normal execution flowing out of the program By default goes to the screen The cout object

Scope

Defines when a variable name is valid

precedence level

Each operator has a ________—operators with higher precedence go first

-input -ouput -cerror

Every program has three streams

Input

Extraction

Initialization

Formally, an initialization is when we give a variable an initial value as part of the declaration

"breaks"

If the next character does not match the type of input we're looking for, the input stream

Input extraction

If the stream is empty, the program pauses and allows the user to type in a new line

Conversion

In an operation that expects two values of the same type - e.g. math and comparison

Initialization

Informally, initializing a variable means giving it a value before using it

Extraction: >> Insertion: <<

Input / Output Operators

Output

Insertion

Characters

Just a number that is intended to be an ASCII value

Assignment Operators

Left hand operand must be a variable (lvalue) Operands must be the same data type Still has a result: the lvalue One time change, not an algebraic rule Beware = when you mean ==

Initialization

Looks like an assignment, but it's different

Const unsigned short/long

Modifiers

Declare ****

Must ____ all variables used in your program

Input extraction

Skips over any whitespace in the stream (throws it away)

input output assignment control flow?

Statements in C++

Redirecting Streams

Streams are like hoses; they can be connected to different sources and destinations

tokens

The basic idea is that input is a stream of ___, not individual characters

Math comparison boolean input/output assignment

Types of operations

Valid Names Declaration Scope Namespaces Initialization

Variables in C++

Scope

Variables in different scopes can have the same name, but it's often a bad idea

text streams

We will be using ______ — data is all ASCII characters (there are also binary streams)

semicolon

each instruction ends with a ____

Comments C style *****

everything btwn /* and */

Comments C++ style ******

from // to the end of the line

broken stream (input)

getting input from a ____ has no effect

Float

has better range, Int has better precision

Range

how big (or small) a number it can hold

Precision

how many significant digits

if (1-way branch)

if (test) block

Two way branch

if (test) block else block

Comments ****

ignored by compiler

#include <iostream>

input/output stream; goes and gets code in iostream so you don't have to keep doing it.

I/O Manipulators—

inserting them into the stream changes the stream

White Space

insignificant; but can't run two words together

String

is in double quotes; represents multiple characters - not the same thing!

Single Character ***

is in single quotes; represents the number for that character

operation on characters

just numbers you can add

unsigned

no negative numbers (integral only); minus

Operators

operate on data to form a result

signed

plus

Output numbers

prints character representation of that number

Output Boolean

prints either "1" or "0" (throwback to C)

Output Characters

prints the character with the given ASCII value

Output insertion

prints whatever you put in stream

Explicit Conversion or TYPE CAST

put the name of the type you want in parenthesis

cerror

screen


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